How 'The Blob' Could Affect Chicago Winter Weather

If you were hoping that this winter would be a mild one, "The Blob" may be bad news for you.

There are many factors that affect the weather, and that includes what is happening in our oceans. In 2014, the NOAA identified a large marine heat wave that dominated the northeast Pacific Ocean. The heat wave lasted until 2016.

Known as "The Blob," "researchers documented many ecological effects associated with the marine heat wave, including unprecedented harmful algal blooms, shifting distributions of marine life, and changes in the marine food web, according to the NOAA.

Related: Thanksgiving Forecast: Old Farmer's Almanac Releases Illinois Weather Predictions

"The 2013 to 2016 event featured warm waters that extended deep into the upper layers of the ocean, which allowed it to persist through the stormy winter months," according to AccuWeather.

And Chicago may have seen the effects too. The winter of 2013-14 was the third-coldest and third-snowiest winter on record. Meteorologists are now wondering what the possible impacts may be from this year's "blob."

"This trailing dip in the jet stream during a warm blob event typically bisects the U.S., driving outbreaks of Arctic air and massive snowfall events into the Chicago area and Upper Midwest," CBS News reported.

This year's marine heat wave is the fourth-largest marine heat wave in the monitored region since monitoring began in 1982, according to NOAA.

In addition to the marine heat wave, a "La Niña" winter is also likely for the fall and early winter of 2025-26. The National Oceanic and Atmospheric Administration has issued a La Niña Watch for the fall and early winter of 2025-26, meaning there is at least a 50 percent chance of a weak La Niña developing later this year.

Related: La Niña Winter Likely: Here's What It Means For Illinois

La Niña is a climate phenomenon that occurs when the central and eastern Pacific Ocean cools down more than usual. It typically causes the northern United States to be cold and wetter than usual, and the southern states to be warmer and drier than usual. That pattern generally extends to Illinois as well. In La Niña conditions, Illinois is usually colder and wetter than normal.

Meteorological winter starts Dec. 1, and only time will tell how cold or snowy this winter will be. According to National Weather Service data, the "normal" first date for a trace or more of snow is Oct. 31. The normal first date for measurable (.1 inch or more) snow is Nov. 18, and the normal first date for one inch or more of snow is Dec. 7.

Also read: ‘Snowy Nor’easters’: Here’s What To Expect From Winter 2025-26 In IL